A large unique data-set has been obtained between 1988 and 1998 in a population of 1400 workers age 30 to 60 years, including an overnight sleep polysomnographic in-lab study conducted on two occasions over an eight year period. We wish to use the statistical power provided by computerized analysis of over 300,000 apneas and hypopneas in this non- clinical population. Our five specific aims are concerned with the causes, consequences and quantitation of sleep disordered breathing (SDB). 1. What are the physiologic characteristics of SDB events in the non-clinical population in terms of severity, high airway resistance, obstructive and central components and associated after- effects on EEG arousal and ventilatory overshoots? Do these important elements of the SDB event change as SDB progresses over time? Do the ventilatory or cardiovascular consequences of apnea or hypopnea and its immediate aftermath determine the likelihood of subsequent sleep- disordered breathing events? 2. What are the immediate and long-term cardiovascular consequences of sleep-disordered breathing events; what characteristics of these SDB events (such as O2 desaturation, arousal, ventilatory overshoot airway resistance, etc.) determine the cardiovascular responses and consequences? 3. What is the effect of aging on SDB and its sequelae as studied in the truly healthy elderly? 4. What role do anatomical characteristics of the upper airway play in determining the frequency and severity I and type of sleep-disordered breathing? Do these anatomical determinants differ in the general non- clinical population versus the obstructive sleep apnea (OSA) population? ... in the obese versus the non-obese? 5. To thoroughly evaluate our computerized analysis of SDB events in order to determine their accuracy and specificity for purposes of quantation and categorization of SDB events.